1. Field of the Invention
The present invention relates to a system for transmitting information on camera accessories, such as an interchangeable lens or a stroboscopic flash device, to a camera body for use by a microprocessor in the camera body without the need for addressing, and particularly to such systems in which the accessory information to be transmitted may vary in content and quantity and is provided to the microprocessor in accordance with an identification code detected for each accessory.
2. Description of the Prior Art
Prior art camera information transmission system employing microprocessors in which memory elements such as a ROM are provided on the side of a camera accessory usable with the camera, such an interchangeable lens or stroboscopic flash, are well known, such as by way of example, the systems described in British Patent No. 1,552,597; U.S. Pat. Nos. 4,509,842; 4,477,164; and 4,560,267; and Japanese Patent Publication Nos. 54-108628 and 59-84228. In such prior art systems, various kinds of information on the camera accessories, such as those regarding an open diaphragm value, a focal length of an interchangeable lens, etc., for instance, are stored in the ROM and the various kinds of information stored therein are read on the side of the main body of a camera. Thus, these prior art systems employ an addressable read only memory or ROM located in the lens or accessory for storing the preset information to be sent to the microprocessor. In this type of system, a camera system has been used so far in which the quantities and contents of information transmitted from the camera accessories to the main body of the camera are defined, information on a given accessory is stored in memory elements such as the ROM in conformity with definitions, and the information on the accessory is read in conformity with the definitions of information on the side of the main body of the camera.
With a view to improving the functions of the main body of the camera and accessories thereof, the quantities of information to be transmitted from the accessories to the main body of the camera tend to increase. This increase in the quantities of information to be transmitted cannot be met by the aforesaid defined quantities, and therefore it becomes necessary to change the defined quantities. When the quantities and contents of the information to be transmitted are changed, however, in the prior art systems a problem occurs in that the camera cannot then normally be employed because of the impossibility of electric transmission of the changed quantity of information, even if accessories having new quantities of information can be fitted to the main body of the original camera. It is also impossible to employ accessories having the former quantities of information for the main body of a camera which reads new quantities of information. In other words, the change in the quantities and contents of information to be transmitted in prior art systems fails to preserve the interchangeability of the camera system, which brings forth a disadvantage to users. There is also a problem to manufacturers that the quantities of information on accessories are limited by the definitions of the quantities and contents of information to be transmitted, thereby depriving them of freedom in development of new products.
In addition to the aforementioned prior art ROM based systems, there have been prior art camera systems which employ simple switches to provide digital information to a microprocessor for use by the microprocessor, such as disclosed in U.S. Pat. Nos. 4,104,649; 4,426,147 and 3,428,858. However, these prior art systems, although not ROM based, still suffer from the same problems as discussed above when the quantities and contents of the information to be transmitted are changed. These disadvantages of the prior art are overcome by the present invention.